A method for changing surface characteristics by forming a film on the material surface has been frequently used in various industrial fields. For instance, by forming an appropriate surface layer additionally on the material surface, it is possible to improve a mechanical strength, to allow electrical insulating properties or conductivity, to allow hydrophile properties, or to improve corrosion resistance.
A heat-exchanger for contacting two fluids having different temperatures from each other to exchange heat has been broadly used in various industrial fields. In particular, a refrigeration air conditioning heat-exchanger additionally uses fin structures for increasing a heat transfer surface of a heat exchanger tube in order to improve heat transfer.
When wet air passes through a heat-exchanger fin, heat transfer occurs between the wet air and a refrigerant of a low temperature supplied through the heat exchanger tube. In this case, when a temperature of the fin surface is lower than a dew-point temperature of the wet air, droplets are condensed on the heat exchanger fin surfaces and the droplets interfere with air flow. Therefore, an operation power of the fan should be increased in order to supply the same flow rate of air, which results in an increase in power consumption.
In the conventional art, a heat exchanger fin structure had an anticorrosive processing performed thereon by using Cr+6 and a silicate-based coating films was formed thereon to thus improve hydrophile properties to allow a condensed water formed on the fin surfaces to easily flow downward. However, in the conventional hydrophilic coating, its hydrophilic characteristics are decreased as time passes.
In addition, in the conventional art, a hydrocarbon polymer film was formed on the heat exchanger fin surfaces to improve hydrophile properties and aging characteristics. However, it was impossible to achieve other advantageous effects such as antibiosis, deodorization or the like. Also, it was inconvenient to perform a separate coating operation for achieving additional advantageous effects.
In the coating film according to the conventional art, on the other hand, uniformity thereof was degraded, and deposition efficiency was lowered during surface processing.